Climate change killed cave bears

Enormous cave bears, Ursus spelaeus, that once inhabited a large swathe of Europe, from Spain to the Urals, died out 27,800 years ago, around 13 millennia earlier than was previously believed, scientists have reported.

The new date coincides with a period of significant climate change, known as the Last Glacial Maximum, when a marked cooling in temperature resulted in the reduction or loss of vegetation forming the main component of the cave bears‘ diet.

They found no convincing evidence of human involvement in the disappearance of these bears. The team used both new data and existing records of radiocarbon dating on cave bear remains to construct their chronology for cave bear extinction.

“Our work shows that the cave bear, among the megafauna that became extinct during the Last Glacial period in Europe, was one of the earliest to disappear,” said Dr Martina Pacher of the Department of Palaeontology at the University of Vienna. “Other, later extinctions happened at different times within the last 15,000 years.”

Many scientists previously claimed that cave bears survived until at least 15,000 years ago, but Dr Pacher and Professor Stuart claim that the methodology of these earlier studies included many errors in dating as well as confusion between cave bear and brown bear remains.

The pair also concluded, from evidence on skull anatomy, bone collagen and teeth, that these extinct mammals were predominantly vegetarian, eating a specialised diet of high-quality plants. Compared with other megafaunal species that would also become extinct, the cave bear had a relatively restricted geographical range, being confined to Europe, which may offer an explanation as to why it died out so much earlier than the rest.

“Its highly specialised mode of life, especially a diet of high-quality plants, and its restricted distribution left it vulnerable to extinction as the climate cooled and its food source diminished,” said Dr Pacher.

The brown bear, with which Ursus spelaeus shares a common ancestor, was spread throughout Europe and much of northern Asia and has survived to the present day.

“A fundamental question to be answered by future research is: why did the brown bear survive to the present day, while the cave bear did not?” said Professor Stuart. Answers to this question may involve different dietary preferences, hibernation strategies, geographical ranges, habitat preferences and perhaps predation by humans.

Cave bears were heavily built animals, with males growing up to around 1000kg. The maximum recorded weight of both Kodiak bears and polar bears – the largest bears living today – is 800kg, with averages of around 500kg.

Scientists have recovered a large quantity of cave bear remains from many cave sites, where they are believed to have died during winter hibernation. Caves provide an ideal environment for the preservation of these remains.

Despite over 200 years of scientific study – beginning in 1794 when a young anatomist, J. Rosenmüller, first described bones from the Zoolithenhöhle in Bavaria as belonging to a new extinct species, which he called cave bear – the timing and cause of its extinction remain controversial.

By far the best source of information on the appearance of cave bears in the flesh is to be found in red pigment cave paintings in the Grotte Chauvet in the Ardèche region of southern France. These are the only depictions in Palaeolithic art that can be attributed unambiguously to the cave bear.

If this is true, then the case of the cave bear is different from other Pleistocene megafauna which became extinct. Contrary to cave bears, the glacial maximum did not kill them. In the case of, eg, the giant deer, the end of the Ice Age meant the growth of forests, which made survival more difficult for them.

Metabolic adaptations to Ice Age Europe may have proved costly to Neanderthals after the continent’s climate started to change, says Patrick Chinnery, a molecular biologist at Newcastle University, UK: here.

A University of Arizona anthropologist has discovered that humans living at a Paleolithic cave site in central Israel between 400,000 and 250,000 years ago were as successful at big-game hunting as were later stone-age hunters at the site, but that the earlier humans shared meat differently: here.

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LONDON: In a new research, scientists from Oxford University have found that giant lions were roaming around Britain, Europe and North America up
to 13,000 years ago.

According to a report by BBC News, the finding came in the form of the remains of giant cats that were earlier thought to be a species of jaguar or tiger, but after DNA analysis, they were proved to be lions.

The Oxford team analysed DNA from fossils and other remains gathered from Germany to Siberia, and Alaska to Wyoming.

They determined that the prehistoric lions were 25 percent bigger than the species of African lion living today, and had longer legs to chase their prey.

They would have lived in icy tundra with mammoth and sabretooth tigers.

It is thought these animals would hunt over longer distances, and their longer legs would help them chase down their prey as opposed to the modern-day species which tends to ambush its victims.

“These ancient lions were like a super-sized version of today’s lions and, in the Americas, with longer legs adapted for endurance running,” said Dr Ross Barnett, who conducted the research at Oxford University’s department of Zoology.

“What our genetic evidence shows is that these ancient extinct lions and the lions of today were very closely related,” he added.

“Cave art also suggests that they formed prides, although the males in the pictures would not have had manes and they are depicted very realistically,” he further added.

The team found that the remains from the Pleistocene Epoch (1.8 million years ago to 10,000 years ago) could be divided into two groups: the American Lion which lived in North America, and the Cave Lion which lived in northern Europe, Russia, Alaska and the Yukon.

These ancient cats would have lived in an environment that was more like an icy tundra and would have shared their habitat with herds of other large animals such as mammoth, woolly rhino, sabre tooth tigers and giant deer.

About 13,000 years ago these species died out in a mass extinction.

Figuring out the reason behind this, Dr Barnett said, was one of the last great scientific mysteries.

“The extinction is a big question that remains unresolved. More research and more advanced genetic analysis may help answer it,” he added.

Thirty-five thousand years before nanotechnology became a buzzword, a different kind of diminutive innovation transformed India. The advent of stone microblades set the stage for the subcontinent’s explosive population growth, new research suggests.

The easy-to-manufacture tools – also known as microliths – were a vast improvement over larger stone flake tools used previously, says Michael Petraglia, an archaeologist at the University of Oxford, UK, who led the study. Because microblades could be cut from stone more quickly and in higher volumes than flakes, hunting probably became a vastly more efficient endeavour.

“It allows people to more reliably and more cheaply slaughter animals,” says Lawrence Guy Straus, a paleoanthropologist at the University of New Mexico in Albuquerque, who was not involved in the study.

Petraglia and his colleagues contend that the beginnings of a global ice age pushed ancient populations of Indians into closer contact – and competition – with one another. “They need to develop new strategies to produce new resources. They invent microlithic technology and it spreads very rapidly.”

Though proving causality of any ancient upheaval is difficult, if not impossible, Petraglia’s team argue that genetic, environmental and archaeological records make a strong circumstantial case for their theory.
Genetic evidence

Between 30 and 35,000 years ago, the Earth cooled dramatically. In Europe, these changes brought with them massive glaciers, pushing Neanderthals and newly arrived humans into small pockets, and perhaps contact.

In India, however, this ice age shortened the monsoon season and transformed what had been a rather homogenous tropical landscape into a patchwork of savannahs and deciduous forests bordered by desert, Petraglia says.

“When you get more deserts you’re getting environmental fragmentation. That is conducive to hunter-gatherers, Petraglia says. “They like mosaic environments because you tend to have a lot of diversity in flora and fauna.”

These changes almost certainly would have split up ancient populations, but they could have spurred their growth as well, Petraglia says. By treating the mitochondrial DNA of contemporary Indians as a sort of molecular clock, the researchers documented an expansion in Indian genetic diversity dated to around the time of this ice age.
Shrinking tools

And this is where microblades come in handy. The tools – narrow and up to 4 centimetres long – began appearing in large numbers around 30,000 years ago, archaeological records from across the subcontinent show. Prior to this, Indians wielded bulkier, less-efficient stone flakes.

Microblades, which were probably attached to spears and later arrows, were a game-changing technology that allowed more densely packed hunter-gatherers to thrive, Petraglia says.

Later innovations – namely agriculture and livestock domestication – undoubtedly pushed population densities higher. But Petraglia thinks that the shifts that occurred 35,000 years ago got the ball rolling. Its influence can still be seen today, he says.
Modern legacy?

“It’s a mystery why there are so many people in that part of the world and it wasn’t just domestication that led to more than a billion people being around in South Asia. We argue that is has to go back to a much earlier period.”

Straus, who mentored Petraglia in the 1980s, buys that argument, but says populations could only swell so much in the ice age period. “We’re still talking about hunter-gatherers; hunter-gatherers are never found in hugely dense numbers,” he says.

Ofer Bar-Yosef, a paleoanthropologist at Harvard University says the discovery of widespread microblade use in India 30,000 years ago “closes an important gap in our knowledge.” Similar tools have been found from around this period in Africa, Europe and west Asia.

But climate change isn’t necessary to spur technological innovation and adoption, Bar-Yosef says. Hominins that predated modern humans wielded stone axes that changed little over hundreds of thousands of years and numerous wild climatic swings.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0810842106)